Nanopillar field-effect and junction transistors with functionalized gate and base electrodes

ABSTRACT

Systems and methods for molecular sensing are described. Molecular sensors are described which are based on field-effect or bipolar junction transistors. These transistors have a nanopillar with a functionalized layer contacted to either the base or the gate electrode. The functional layer can bind molecules, which causes an electrical signal in the sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/675,637, filed on Jul. 25, 2012, the disclosure ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to semiconductor structures for molecularsensing applications. More particularly, it relates to transistors withfunctionalized gate and/or base electrodes.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description of exampleembodiments, serve to explain the principles and implementations of thedisclosure.

FIG. 1 depicts a cross-section geometry of an exemplary embodiment of afield-effect transistor with a functionalized gate.

FIG. 2 depicts an exemplary embodiment of a MOSFET with antibodies boundto the functionalized gate.

FIG. 3 depicts an exemplary embodiment of a MOSFET with antigens boundto antibodies on the functionalized gate.

FIG. 4 depicts an exemplary embodiment of a jFET sensor.

FIG. 5 depicts an exemplary embodiment of a BJT sensor.

FIG. 6 depicts an exemplary embodiment of a circuit to sense the signalfrom a field-effect transistor sensor.

SUMMARY

According to a first aspect of the disclosure, a structure for sensingmolecules is described, the structure comprising: a semiconductorsubstrate; a source region in the semiconductor substrate, the sourceregion comprising a first doped semiconductor region; a drain region inthe semiconductor substrate, the drain region comprising a second dopedsemiconductor region; a source electrode, contacted to the sourceregion; a drain electrode, contacted to the drain region; an insulatinglayer, covering at least in part the source electrode, and/or the drainelectrode, and/or the source region, and/or the drain region, and/or thesemiconductor substrate; an oxide layer, covering a substrate regionbetween the source region and the drain region; a nanopillar gateregion, contacting the oxide layer; and a functionalized layer on top ofthe nanopillar.

According to a second aspect of the disclosure, a structure for sensingmolecules is described, the structure comprising: a semiconductorsubstrate; an emitter region in the semiconductor substrate, the emitterregion comprising a first doped semiconductor region; a base region inthe semiconductor substrate, the base region comprising a second dopedsemiconductor region; a collector region in the semiconductor substrate,the collector region comprising a third doped semiconductor region; anemitter electrode, contacted to the emitter region; a collectorelectrode, contacted to the collector region; a nanopillar, contactingthe base region; and a functionalized layer on top of the nanopillar.

According to a third aspect of the disclosure, a structure for sensingmolecules is described, the structure comprising: a semiconductorsubstrate; a source region in the semiconductor substrate, the sourceregion comprising a first doped semiconductor region; a drain region inthe semiconductor substrate, the drain region comprising a second dopedsemiconductor region; a source electrode, contacted to the sourceregion; a drain electrode, contacted to the drain region; an insulatinglayer, covering at least in part the source electrode, and/or the drainelectrode, and/or the source region, and/or the drain region, and/or thesemiconductor substrate; a nanopillar gate region, contacting asubstrate region between the source region and the drain region; and afunctionalized layer on top of the nanopillar.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Described herein are various embodiments in the field of electronicsthat are directed at the detection of a specific target.

The terms “detect” or “detection” as used herein indicates thedetermination of the existence, presence or fact of a specific target ina limited portion of space, including but not limited to a sample, areaction mixture, or other limited portion of space identifiable to askilled person upon a reading of the present disclosure. The detectioncan be quantitative or qualitative. A detection is “quantitative” whenit refers to, relates to, or involves the measurement of quantity oramount of the target or signal (also referred as quantitation), whichincludes but is not limited to any analysis designed to determine theamounts or proportions of the target or signal. Detection is“qualitative” when it refers to, relates to, or involves identificationof a quality or kind of the target or signal in terms of relativeabundance to another target or signal, which is not quantified.

The term “target” as used herein indicates an analyte of interest thatis to be detected. The term “analyte” refers to a substance, compound,moiety, or component whose presence or absence in a sample is to bedetected. Analytes include but are not limited to molecules andbiomolecules. The term “biomolecule” as used herein indicates asubstance, compound or component associated with a biologicalenvironment including but not limited to sugars, amino acids, peptides,proteins, and oligonucleotides/nucleic acids.

In the field of electronics, transistors have been used asvoltage-current and current-current transducers. For molecular sensingapplications, it is known that certain molecules bind effectively tometals when those metals are functionalized by chemical and/orbiological agents. In some cases, molecules can even bind to metalswithout any additional layer. In the present disclosure, methods anddevices are described, where transistors are actuated by non-electronicmeans, by functionalizing the terminal contacts of the transistors, forexample gate, base, and drain of a MOSFET, with chemical and biologicalagents. Any number of contacts can be functionalized, from only one toall of them. By functionalizing the gate/base of nanopillar transistors,it is possible to sense biological and chemical targets of interest.

Nano-scale fabrication allows for the fabrication of transistors invarious shapes and sizes. For instance, silicon features can be etchedin high height:width aspect ratios. Nanopillar structures with aspectratios ranging from 1:1 to 100:1 can be used to create high surface areacontacts. A high surface area contact can be advantageous for molecularsensing applications. These transistors structures can be further shapedto create a variety of three-dimensional geometries. Some geometries canbe more efficient at sensing certain molecules, or in specific sensingenvironments. Nanopillar transistors can be fabricated by standardsemiconductor fabrication techniques, commonly known to the personskilled in the art.

In some embodiments, the binding compound for capturing a target fordetection can be an antibody. The term “antibody” as used herein refersto a protein of the kind that is produced by activated B cells afterstimulation by an antigen and can bind specifically to the antigenpromoting an immune response in biological systems. Full antibodiestypically consist of four subunits including two heavy chains and twolight chains. The term antibody includes natural and syntheticantibodies, including but not limited to monoclonal antibodies,polyclonal antibodies or fragments thereof or derivative thereof. Theterms “fragment” as used herein with reference to antibody indicates anyportion of an antibody that retain an immunogenic activitycharacteristic of the antibody. The term “derivative” as used hereinwith reference to an antibody, indicates a molecule that is structurallyrelated to the antibody and is derivable from the antibody by amodification that introduces a feature that is not present in theantibody while retaining functional properties of the antibody.Accordingly, a derivative antibody, or of any fragment thereof, FaB orscFv, usually differs from the original antibody or fragment thereof bymodification of the amino acidic sequence that might or might not beassociated with an additional function not present in the originalantibody or fragment thereof. Methods to provide derivative and to testthe ability of the derivative to retain the one or more functionalproperties are identifiable by a skilled person. Exemplary antibodiesinclude IgA, IgD, IgG1, IgG2, IgG3, IgM and the like. Exemplaryfragments include Fab Fv, Fab′ F(ab′)2 scFV, single chain antibodies andthe like. A monoclonal antibody is an antibody that specifically bindsto and is thereby defined as complementary to a single particularspatial and polar organization of another biomolecule which is termed an“epitope”. In some forms, monoclonal antibodies can also have the samestructure. A polyclonal antibody refers to a mixture of differentmonoclonal antibodies. In some forms, polyclonal antibodies can be amixture of monoclonal antibodies where at least two of the monoclonalantibodies binding to a different antigenic epitope. The differentantigenic epitopes can be on the same target, different targets, or acombination. Antibodies can be prepared by techniques that are wellknown in the art, such as immunization of a host and collection of sera(polyclonal) or by preparing continuous hybridoma cell lines andcollecting the secreted protein (monoclonal).

The term “binding compound” or “capture agent’ as used herein indicatesa molecule that can specifically bind to a target, e.g. through thespecific binding of one or more of molecule binding sites. Bindingcompounds herein described can include molecules of various chemicalnatures such as polypeptides (e.g. antibodies or receptors),polynucleotides (e.g. DNA or RNA) and/or small molecules (e.g.aptamers), as well as other molecules capable of specific bindingidentifiable by a skilled person upon reading of the present disclosure.In some embodiments, an antibody or antibody fragment can be used tospecifically bind or capture a molecule for detection.

In some embodiments the target and/or the binding compound for detectioncan be a protein or a polynucleotide. The term “protein” as used hereinindicates a polypeptide with a particular secondary and tertiarystructure that can interact with and in particular bind another analyteand in particular, with other biomolecules including other proteins,DNA, RNA, lipids, metabolites, hormones, chemokines, and smallmolecules. The term “polypeptide” as used herein indicates an amino acidpolymer of any length including full length proteins and peptides, aswell as analogs and fragments thereof. A polypeptide of three or moreamino acids is also called a protein oligomer, peptide or oligopeptide.In particular, the terms “peptide” and “oligopeptide” usually indicate apolypeptide with less than 50 amino acid monomers. As used herein theterm “amino acid”, “amino acidic monomer”, or “amino acid residue”refers to any of the twenty naturally occurring amino acids, non-naturalamino acids, and artificial amino acids and includes both D an L opticalisomers.

The term “polynucleotide” as used herein indicates an organic polymercomposed of two or more monomers including nucleotides, nucleosides oranalogs thereof. The term “nucleotide” refers to any of severalcompounds that consist of a ribose or deoxyribose sugar joined to apurine or pyrimidine base and to a phosphate group and that is the basicstructural unit of nucleic acids. The term “nucleoside” refers to acompound (such as guanosine or adenosine) that consists of a purine orpyrimidine base combined with deoxyribose or ribose and is foundespecially in nucleic acids. The term “nucleotide analog” or “nucleosideanalog” refers respectively to a nucleotide or nucleoside in which oneor more individual atoms have been replaced with a different atom orwith a different functional group. Accordingly, the term“polynucleotide” includes nucleic acids of any length, and in particularDNA, RNA, analogs and fragments thereof.

FIG. 1 illustrates an embodiment of a nanopillarmetal-oxide-semiconductor field-effect transistor (MOSFET) with afunctionalized gate, which can be used for molecular sensing (100). Thesemiconductor sensor (100) can be fabricated using standard CMOSfabrication techniques, as well as innovative techniques in pinch-offoxidation and electron-beam annealing of dopants which are known to theperson skilled in the art.

The structure (100) of FIG. 1 is fabricated on a semiconductor substrate(105). For example, a silicon substrate can be used, but also othersemiconductors can be used as understood by the person skilled in theart. The structure (100) includes a source (110) and a drain (112). Thesource (110) and drain (112) may be fabricated, for example, by dopingthe substrate (105). The source (110) and drain (112) can be contactedelectrically by electrical interconnects (114) for the source and (116)for the drain. For example, contacts (114) and (116) may be fabricatedwith metals.

A passivation layer (120) prevents unwanted electrical conduction withcontacts (114) and (116). An insulating layer (122) may surround thesubstrate (105) for insulating purposes. By way of example and not oflimitation, the insulating layer (122) may be silicon oxide, for thecase of silicon substrates.

The gate structure (130) of the MOSFET sensor can have differentgeometries. The example of FIG. 1 is intended as exemplary, and othershapes can be used. Different height:width aspect ratios may be used,depending on the application. The gate (130) can be surrounded by aninsulating layer (135), for example silicon oxide for the case ofsilicon substrates.

The structure (100) can comprise a functionalized layer (140). Suchlayer can have different compositions. It can be a single metalliclayer, for example gold, as some molecules are known in the art tofunctionally bind to gold. Other functionalized layers can be used,which may bind to a wider or narrower range of molecules. Molecules ofinterest can comprise gases such as nitrogen, as well as biologicalmolecules of interest in biosensing application, such as, for example,polynucleotides or proteins. The functionalized layer (140) can be asingle layer, or a composite layer such as a matrix includingnanoparticles, or a multiple layer structure, such as a bilayer.

In another example, DNA can be linked to gold or platinum nanoparticleson the functionalized layer and can be used in the specific capture ofprotein. Procedures can be done to immobilize DNA or RNA to the gold orplatinum surface through a thiol linker, as is known to persons skilledin the art. Surface immobilization of nucleic acids can be used as abiosensor assay in order to capture specific nucleic acid bindingproteins, or if the nucleic acid that is bound to the layer is singlestranded, it can be used to bind its hybridization partner in solution.When target molecules bind to the functionalized layer, the voltagesignal caused by the binding of the molecules triggers a signal currentin the circuit, as can be understood by the person skilled in the art.The test for specific protein binding can be assayed by using differentlengths of the specific DNA bound to the layer in order to verify thebinding characteristics of the protein in question.

When a target molecule binds to the functionalized layer (140), anelectric charge is induced in the gate (130), leading to the formationof an inversion channel underneath the gate oxide (135). The gate oxide(135) electrically insulates the gate (135) from the substrate (105),the source (110) and the drain (112). The mechanism leading to aformation of an inversion channel underneath the gate (135) mimics thestandard mode of operation of MOSFETs, which is well known to the personskilled the art.

By modulating the concentration of a target molecule at thefunctionalized layer (140) of gate (130), it is possible to transduce arange of currents from the source (110) to the drain (116). In this way,it is possible to detect and amplify concentrations of target moleculesin an analyte of interest. Therefore, it can be possible, for example,to detect concentrations of molecules in a liquid, or gas.

FIG. 2 illustrates an exemplary embodiment of the structure of FIG. 1with an antibody-functionalized layer on the gate. Antibodies (205) arebound to the functionalized gate electrode (210).

FIG. 3 illustrates an exemplary embodiment of antigen capture. Anantigen (305) binds to an antibody (310) on the functionalized layer(315). When an antigen (305) binds to an antibody (310) on thefunctionalized layer (315), an electric charge is induced in the gate(320), leading to the formation of an inversion channel (325) underneaththe gate oxide (330). Through such method, an electrical signal istriggered through the formation of an inversion channel (325) in theMOSFET, which is associated with the binding of molecules on thefunctionalized layer (315).

FIG. 4 illustrates another exemplary embodiment, where the nanopillartransistor (400) has no gate oxide. In this embodiment, an electricfield between the pillar head (405) and the substrate (410) can modulatethe current from the source (415) to the drain (420). As it is known tothe person skilled in the art, this mode of operation mimics a junctionfield effect transistor (jFET). Such a transistor can be functionalized,through a functionalized layer (425), with biological and chemicalagents for target detection, similarly to the other embodiments of thisdisclosure.

FIG. 5 illustrates a further exemplary embodiment, where the sensor(500) is based on a nanopillar bipolar junction transistor (BJT) with afunctionalized base electrode. In this configuration, the emitter (505),base (510) and collector (515) form a bipolar junction transistor, asknown by the person skilled in the art. For example, the emitter (505)can be an n-doped semiconductor, the base (510) can be a p-dopedsemiconductor, and the collector (515) can be an n-doped semiconductor.The emitter is electrically contacted by a contact (520), for example ametal, while the collector is contacted by a contact (525). A nanopillar(530) is contacted to the base (510). A functionalized layer (535) canbe present on top of the nanopillar (530). The functionalized layer canoperate similarly to the other embodiments of the disclosure, such as inFIG. 3. The functionalized layer (535) can be fabricated on top of thenanopillar (530), or on the sides. The nanopillar can have differentshapes, not limited to rectangular, cylindrical and tapered. When atarget molecule is captured by the functionalized layer (535), a currentis injected into the base region (510), which can cause the BJT tooperate in forward active conduction. Therefore, an electrical signal isassociated with the presence of specific target molecules on thefunctionalized layer (535).

In the embodiments described in the disclosure, an electrode triggers anelectrical signal when a molecule is captured by a functionalized layer,such as layer (535) in FIG. 5, or layer (315) in FIG. 3. This electrodecan be composed of a variety of materials, including (but not limitedto), silicon, silicon oxide, sapphire, aluminum, copper, rhodium,gallium, palladium, platinum, iridium, Ag—AgCl, and gold. Properselection of electrode material will allow for selective binding ofchemical and biological agents to the target molecules, allowing forelectrical detection of target molecules of interest. Alternatively, thegate electrode material can be used to directly facilitateelectrochemical reactions on its surface. For example, Pt—PtRu gatecontacts can be used to characterize methanol oxidation/reduction.

The method described in the disclosure can be extended to allow forother types of detection. For example, bonding of chemical andbiological agents to the functionalized layers described in thedisclosure can be used for detection of different target molecules,including (but not limited to), hydrocarbon groups for glucosedetection, hydrocarbon membranes for methanol detection, and chemicalstructures for H₃O⁺ and H⁺ detection.

In other embodiments, the functionalized layer comprises chi-selectiveand epsilon-selective materials. The method of the disclosures can befurther used for magnetic and electrical detection of a variety oftarget molecules (e.g. hemoglobin, DNA).

In one embodiment, a configuration of a nanopillar MOSFET transistorinvolves the functionalization of the gate electrode with monoclonalantibodies. These antibodies are bound to the gate electrode usingepoxide chemistries. When the antigen capture occurs, there will be aconformational change in the structure of the antibody. Thisconformational change, in conjunction with the proximity of the targetantigen to the gate, induces a charge in the gate electrode. This chargecreates a channel below the gate oxide, turning ON the MOSFET.

By way of example and not of limitation, the antibodies attached to thefunctionalized layer of FIG. 2 and FIG. 3 can also be used to indirectlycapture targets by initially being bound to a specific antigen that isspecific for binding a particular molecule. The antigen that is specificfor binding a particular molecule can have multiple binding sites thatare not affected in binding a specific molecule when it is bound to theantibody on the functionalized layer. Said molecule of interest can be aspecific nucleic acid sequence, such as one of DNA or RNA sequence, or aparticular protein of interest. When the antigen that is bound to theantibody captures a specific molecule of interest, a conformationalchange occurs in the structure of the antigen that is translated to thebound antibody, thus inducing a charge in the gate electrode, therebycreating a channel below the gate oxide, turning ON the MOSFET. By wayof example and not of limitation, a DNA binding protein such as atranscription factor can be bound to the antibody in order to capture aspecific DNA sequence.

The fabrication of the nanopillar transistors can be completely CMOScompatible, a clear advantage as known to the person skilled in the art,as it allows for the integration of the functionalized transistors withconventional transistors on a single semiconductor substrate. Forinstance, a functionalized nanopillar FET can be contacted with CMOStransistors to code for a small signal gate voltage into a large signalcurrent. An exemplary circuit to realize this embodiment is illustratedin FIG. 6. In FIG. 6, a functionalized-gate p-channel field effecttransistor (605) is shown. A source voltage (610) and drain voltage(615) are provided for the operation of circuit (600).

When target molecules bind to the functionalized layer of transistor(605), the voltage signal caused by the binding of the moleculestriggers a signal current in the circuit (600), as can be understood bythe person skilled in the art. Since the nanopillar transistors can becompatible with CMOS fabrication techniques, a monolithic integration offunctionalized transistors with conventional electronics on singlesemiconducting substrate is possible.

The examples set forth above are provided to those of ordinary skill inthe art a complete disclosure and description of how to make and use theembodiments of the gamut mapping of the disclosure, and are not intendedto limit the scope of what the inventor/inventors regard as theirdisclosure.

Modifications of the above-described modes for carrying out the methodsand systems herein disclosed are obvious to persons of skill in the artand are intended to be within the scope of the following claims. Allpatents and publications mentioned in the specification are indicativeof the levels of skill of those skilled in the art to which thedisclosure pertains. All references cited in this disclosure areincorporated by reference to the same extent as if each reference hadbeen incorporated by reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. A structure for sensing molecules, the structurecomprising: a semiconductor substrate; a source region in thesemiconductor substrate, the source region comprising a first dopedsemiconductor region; a drain region in the semiconductor substrate, thedrain region comprising a second doped semiconductor region; a sourceelectrode, contacted to the source region; a drain electrode, contactedto the drain region; an insulating layer, covering at least in part thesource electrode, and/or the drain electrode, and/or the source region,and/or the drain region, and/or the semiconductor substrate; an oxidelayer, covering a substrate region between the source region and thedrain region; a nanopillar gate region, contacting the oxide layer; anda functionalized layer on top of the nanopillar.
 2. The structure ofclaim 1, wherein the shape of the nanopillar gate region comprises acylindrical shape, a rectangular shape, or a tapered shape.
 3. Thestructure of claim 1, wherein the functionalized layer comprises twolayers, or a matrix layer containing nanoparticles.
 4. The structure ofclaim 1, wherein the nanopillar gate region is contacted through a toplayer from a material chosen among silicon, silicon oxide, sapphire,aluminum, copper, rhodium, gallium, palladium, platinum, iridium,Ag—AgCl, gold, and Pt—PtRu.
 5. The structure of claim 1, wherein thenanopillar gate region can be used to directly facilitateelectrochemical reactions on its surface.
 6. The structure of claim 1,wherein the functionalized layer comprises antibodies for antigencapture.
 7. The structure of claim 1, wherein the functionalized layercan bind to molecules, wherein the molecules comprise chemical andbiological molecules.
 8. The structure of claim 7, wherein thebiological molecules comprise DNA.
 9. A method for detecting moleculeswith the structure of claim 1, the method comprising: providing a gasand/or fluid solution; contacting the solution to the functionalizedlayer; detecting an electrical signal between the source region and thedrain region.
 10. A structure for sensing molecules, the structurecomprising: a semiconductor substrate; an emitter region in thesemiconductor substrate, the emitter region comprising a first dopedsemiconductor region; a base region in the semiconductor substrate, thebase region comprising a second doped semiconductor region; a collectorregion in the semiconductor substrate, the collector region comprising athird doped semiconductor region; an emitter electrode, contacted to theemitter region; a collector electrode, contacted to the collectorregion; a nanopillar, contacting the base region; and a functionalizedlayer on top of the nanopillar.
 11. The structure of claim 10, whereinthe shape of the nanopillar comprises a cylindrical shape, a rectangularshape, or a tapered shape.
 12. The structure of claim 10, wherein thefunctionalized layer comprises two layers, or a matrix layer containingnanoparticles.
 13. The structure of claim 10, wherein the nanopillar iscontacted through a top layer from a material chosen among silicon,silicon oxide, sapphire, aluminum, copper, rhodium, gallium, palladium,platinum, iridium, Ag—AgCl, gold, and Pt—PtRu.
 14. The structure ofclaim 10, wherein the nanopillar can be used to directly facilitateelectrochemical reactions on its surface.
 15. The structure of claim 10,wherein the functionalized layer comprises antibodies for antigencapture.
 16. The structure of claim 10, wherein the functionalized layercan bind to molecules, wherein the molecules comprise chemical andbiological molecules.
 17. The structure of claim 16, wherein thebiological molecules comprise DNA.
 18. A method for detecting moleculeswith the structure of claim 10, the method comprising: providing a gasand/or fluid solution; contacting the solution to the functionalizedlayer; detecting an electrical signal between the emitter region and thecollector region.
 19. A structure for sensing molecules, the structurecomprising: a semiconductor substrate; a source region in thesemiconductor substrate, the source region comprising a first dopedsemiconductor region; a drain region in the semiconductor substrate, thedrain region comprising a second doped semiconductor region; a sourceelectrode, contacted to the source region; a drain electrode, contactedto the drain region; an insulating layer, covering at least in part thesource electrode, and/or the drain electrode, and/or the source region,and/or the drain region, and/or the semiconductor substrate; ananopillar gate region, contacting a substrate region between the sourceregion and the drain region; and a functionalized layer on top of thenanopillar.
 20. The structure of claim 19, wherein the shape of thenanopillar gate region comprises a cylindrical shape, a rectangularshape, or a tapered shape.
 21. The structure of claim 19, wherein thefunctionalized layer comprises two layers, or a matrix layer containingnanoparticles.
 22. The structure of claim 19, wherein the nanopillargate region is contacted through a top layer from a material chosenamong silicon, silicon oxide, sapphire, aluminum, copper, rhodium,gallium, palladium, platinum, iridium, Ag—AgCl, gold, and Pt—PtRu. 23.The structure of claim 19, wherein the nanopillar gate region can beused to directly facilitate electrochemical reactions on its surface.24. The structure of claim 19, wherein the functionalized layercomprises antibodies for antigen capture.
 25. The structure of claim 19,wherein the functionalized layer can bind to molecules, wherein themolecules comprise chemical and biological molecules.
 26. The structureof claim 25, wherein the biological molecules comprise DNA.
 27. A methodfor detecting molecules with the structure of claim 19, the methodcomprising: providing a gas and/or fluid solution; contacting thesolution to the functionalized layer; detecting an electrical signalbetween the source region and the drain region.